Fall Colours – Why do leaves change?

Fall Colours – Why do leaves change?

Fall colours – Why leaves change?

Fall is one of the most beautiful and colourful times of the year. Symbolizing the end of summer and the beginning of winter. So why do they change and what happens within the leaves to cause this change.

Well, deciduous trees, like Birch trees, need to store nutrients in their roots throughout the summer. This is to survive the winter and have enough energy for spring. During the summer months leaves are bright green, because of the pigment called chlorophyll. Chlorophyll is essential in converting sunlight, water and carbon dioxide into glucose through the process we know as photosynthesis. Nutrients such as nitrogen and phosphorus are also found in high quantities in the summer foliage.

As the summer season progresses and cooler temperature set in, changes in weather patterns, such as rainfall levels, and less daylight hours occur. These elements trigger a change in the leaves; the tree begins to absorb the last of the chlorophyll, and the leaves start to change colour.

So why do some trees turn yellow and others red?

Well, yellow colours appear when the chlorophyl is broken down and absorbed by the tree, unveiling the yellow pigments called carotenoids. Carotenoids are interesting because they protect the leaves from the byproducts of photosynthesis.

Anthocyanins are the pigmentation in the leaves that turn red, like those of the maple trees that turn red in Ontario. This is interesting as this red pigment is actually created by the tree to protect the leaves from direct sunlight. Because when nutrients are transferred from the leave to the roots, the leaves become susceptible to sunlight.

So why don’t all deciduous tree turn red?

Here is the interesting part! Those trees who turn yellow are trees that are called pioneer species and are the first to inhabit open landscapes; therefore are geared to be tolerant towards direct sunlight! This was discouvered by a plant science researcher called Bill Hoch.

A beautiful hike in Wells Gray Park to enjoy the fall colours is the West Lake Loop. Here you can also view the the Chinook Salmon in their final efforts against the strong currents of Bailey’s Chute.

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